Optical network regenerator bypass module and associated method

ABSTRACT

An optical bypass element for an optical communication system. The optical bypass element, formed of an optical interleaver, is positioned in parallel with a regenerator. Data requiring regeneration is caused to be provided to the regenerator while data not requiring regeneration is bypassed about the regenerator by way of the optical bypass element. Once bypassed around the regenerator and once regenerated at the regenerator, the respective data is recombined and subsequently routed to communication endpoints.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims the priority of Provisional PatentApplication No. 60/715,427, filed on Sep. 9, 2005, the contents of whichare incorporated herein by reference.

The present invention relates generally to an optical communicationsystem in which wavelength division multiplexed (WDM) data iscommunicated. More particularly, the present invention relates toapparatus, and an associated method, that provides routing of firstoptical data of the WDM data around a regenerator, while permittingsecond optical data of the WDM data to be applied to the regenerator.

An optical communication system is formed with line terminatingequipment within which Electrical-Optical (E-O) and Optical-Electrical(O-E) having two or more different transmission performancecharacteristics are deployed. Viz., the system includes a network partthat requires optical data to be communicated with relatively lowtransmission impairments and a new network part, permitting ofcommunication of optical data with higher transmission impairments.Optical data communicated in the legacy network is caused to be appliedto the optical regenerator while the optical data communicated by way ofthe new network part is bypassed around the optical regenerator. Datathat need not be optically regenerated is bypassed around theregenerator while data that needs to be regenerated is applied to theregenerator.

BACKGROUND OF THE INVENTION

Much attention has been directed towards optical communicationtechnologies in efforts to develop and to deploy optical communicationsystems through which to communicate data. Chief amongst the advantagesof an optical communication system is the capability of transportingvery large amounts of data at very high data throughput rates. Anoptical communication system typically is formed of a fiber opticnetwork having optical fibers through which optical energy iscommunicated to communicate data between communication endpoints.Wavelength division multiplexing (WDM) is a conventional technique usedto modulate the data that is to be communicated between thecommunication endpoints. In a typical optical communication system anoptical fiber transports optical data on many different communicationchannels, defined in terms of wavelength or frequency. Data is modulatedupon optical carriers of different wavelengths, thereby providing, oneach optical fiber, multi-channel communications.

As in any communication system, a receiving endpoint must be able torecreate the informational content of the communicated data. The data,when delivered to the communication endpoint, must, therefore, be ofsufficient quality that the informational content of the data may stillbe recovered. Examples of transmission impairments which might result inthe quality of the received signal being impacted are signal to noiseratio, chromatic dispersion, polarization mode dispersion and self phasemodulation. The degree to which a received signal quality will bereduced by these impairments is dependent on the data being transmittedand the specific characteristics of the E-O and O-E converters at eachend of the transmission system.

Advancements in optical communication technologies have resulted in theresilience of O-E and E-O converters being able to operate over systemswith greater transmission impairments

Additions to an existing optical communication system are sometimesmade. Additions are made, for instance, when the system is expanded toencompass a new area, such as a new building or new development. And,sometimes, parts of an optical communication system are upgraded,leaving remaining parts operable as originally-implemented. When the newnetwork parts are added to the existing network, the signals generatedthereon are sometimes generated on wavelengths set-off from, andinterleaved with, the wavelengths used by the existing, i.e., legacynetwork part. The communication capacity of the network is increased,but without a corresponding increase in the total optical bandwidth overwhich the signals are communicated.

Optical communication systems sometimes include devices, referred to asregenerators, that regenerate optical signals by performing anOptical-Electrical-Optical (O-E-O) conversion. Regenerators aretypically installed where the transmission impairments in the systemhave reached the threshold for acceptable performance for one or more ofthe channels being carried. A legacy communication system may requiretransmission impairments which are lower than newer communicationsystems and are therefore more likely to require the use of, oradditional numbers of, regenerators than would be required in newersystems. When an optical communication system is formed of legacynetwork parts and new network parts, the different network parts includecommon paths that extend to an optical regenerator. Some of the opticaldata delivered to the regenerator must be regenerated by theregenerator, but other parts of the optical data need not be regeneratedby the regenerator.

Regeneration of optical data not necessitating regeneration entailsneedless expense in furnishing the O-E-O regeneration converters at theregenerator site. A scheme by which only the data requiring regenerationpass through the O-E-O converters at a regenerator site would thereforebe advantageous.

It is in light of this background information relating to communicationof optical data in an optical communication system that the significantimprovements of the present invention have evolved.

SUMMARY OF THE INVENTION

The present invention, accordingly, advantageously provides apparatus,and an associated method, for an optical communication system in whichwavelength division multiplexed data is communicated.

Through operation of an embodiment of the present invention, a manner isprovided by which optical data carried on some of the WDM wavelengthsmay be selected for regeneration if required while data not requiringregeneration may pass through the regenerator site without undergoingO-E-O regeneration if the data is of a form which does not requireregeneration at the regenerator site. When, for instance, an opticalcommunication system is formed of a legacy network portion and a newnetwork portion that exhibit different transmission requirements, theoptical data communicated by way of the legacy network portion isapplied to the regenerator while the optical data communicated by way ofthe new network part bypasses the regenerator.

Wavelength division multiplexed data communicated by way of separateparts of the optical communication system is applied to, or bypassedaround, the regenerator. Optical data regenerated by the regenerator andoptical data bypassed around the regenerator are subsequently recombinedby way of a multiplexer.

In another aspect of the present invention, an optical bypass ispositioned, in-line with a fiber upon which first optical data andsecond optical data is transported. The optical bypass element isfurther positioned in parallel with an optical regenerator. The opticalbypass element forms, for instance, an optical interleaver that passesoptical data of first wavelengths. When the first optical data,communicated by way of a new optical network portion, is modulated to beof the first wavelengths, the optical data, when delivered to theregenerator, bypasses the regenerator as the optical interleaver permitsthe optical data to pass there through. When the second optical data,communicated by way of the legacy network part, is modulated to be ofthe second wavelength, the data, when delivered to the regenerator, isregenerated at the regenerator. Through appropriate selection of thecharacteristics of the optical interleaver and appropriate modulation ofthe optical data transported by way of the separate network parts,optical data needing to be regenerated is regenerated, and optical datathat does not necessitate regeneration is bypassed around theregenerator. Unnecessary regeneration of optical data is thereby avoidedwhile also permitting optical data that requires regeneration to beregenerated by the regenerator.

In another aspect of the present invention, a recombiner is provided torecombine the bypassed optical data with the data regenerated at theregenerator through the provision of a path extending from the opticalbypass element to a multiplexer that multiplexes together theregenerated data with the bypassed data.

The regenerator forms an O-E-O configuration and, the regenerator mayinclude, for instance, a set of couplers to which the optical bypasselement is coupled and to which the recombiner extends and thereby toprovide a bypass path about the optical regenerator. Additional pathsare formable to provide for subsequent channel path expansion.

The optical interleaver provides a passive element that permitsbypassing of optical data of selected wavelengths about the regenerator.When the multiplexing is appropriately configured to communicate opticaldata in a legacy network part at one wavelength or frequency, or set ofwavelengths (frequencies), and new-network optical data to becommunicated at a second, or second set of, optical wavelengths(frequencies), the data parts necessitating regeneration are regeneratedby the optical regenerator, while data parts not needing regenerationare bypassed around the regenerator.

In these and other aspects, therefore, apparatus, and an associatedmethod, is provided for an optical network. The optical network has aregenerator to which first optical data is routed and to which secondoptical data is routed. An optical bypasser is positioned in-line withpaths upon which the first optical data and the second optical data arerouted and in parallel with the regenerator. The optical bypasser isconfigured to route the first optical data through for regeneration.And, the optical bypasser is configured to permit routing of the secondoptical data to bypass the regenerator. A recombiner is positionedin-line with the optical bypasser. The recombiner is configured torecombine routing paths of the first optical data, regenerated by theregenerator, and the second optical data bypassed around theregenerator.

A more complete appreciation of the present invention and the scopethereof can be obtained from the accompanying drawings that are brieflysummarized below, the following detailed description of thepresently-preferred embodiments of the present invention, and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional block diagram of an opticalcommunication system in which an embodiment of the present invention isoperable.

FIG. 2 illustrates a diagram representative of operation of the bypasselement and the regenerator that form part of the optical communicationsystem shown in FIG. 1.

FIG. 3 illustrates a partial process flow, partial functional block,diagram representative of operation of an embodiment of the presentinvention.

FIG. 4 illustrates a method flow diagram representative of the method ofoperation of an embodiment of the present invention.

DETAILED DESCRIPTION

Referring first to FIG. 1, an optical communication system, showngenerally at 10, provides for the communication of data between lineterminating equipment, here represented by, and described in terms ofsets of, communication stations forming communication endpoints. Here,two sets of communication stations forming communication endpoints areshown. The communication stations 12 and 14 form a communication stationpair between which first optical data is communicated, and thecommunication stations 16 and 18 are representative of a second pair ofcommunication stations between which second optical data iscommunicated. The sets formed of the communication stations 12-14 and16-18 are merely exemplary. Other numbers of, and other combinations of,communication stations are capable of forming communication endpointsbetween which data is communicated pursuant to operation of thecommunication system.

Here, the communication system includes both a legacy network portionand a new network portion. The legacy network portion of thecommunication system requires that data-containing signals exhibit lowertransmission impairments than the corresponding signals transported byway of the new network portion of the communication system. In systemswhere the impairments exceed the threshold at which the informationalcontent of the data is accurately recoverable optical regenerators aresometimes used. In the figure, an optical regenerator 24, a legacyregeneration station, is representative of an optical regenerator usedto regenerate a data-containing optical signal provided thereto suchthat the regenerated signal is of improved OSNR, or other,characteristic. Optical data, provided to the regenerator 24 by way ofthe line 26, an optical path, i.e., fiber, is regenerated andregenerated data is formed on the line 28. The optical regenerator, inthe exemplary implementation, forms an O-E-O(optical-electrical-optical) 3R regenerator. In alternateimplementations, the regenerator may form a 2R-regenerator. In anyexemplary implementation, however, the regenerator forms amultiple-wavelength channel regenerator.

The exemplary regenerator 24, shown in FIG. 1, includes a demultiplexer32 and multiplexer 34 set that includes a plurality of lines 36 eachcontaining transponders 38 that perform 3R regeneration of therespective lines. Collocated at the regenerator site there are alsoshown amplifier elements 41 and 42 that form optical pre-amplifier andpost-amplifier elements, respectively. And here, the regenerator alsoincludes splitters 44 and 46.

The optical system further includes a plurality of additional amplifiers58. The optical system is further shown to include an optical signalmultiplexer 62 and optical signal demultiplexer 64.

The multiplexer 62 receives optical signals on a plurality of lines 68and combines them to form a multi-channel signal WDM (WavelengthDivision Multiplex) signal, formed on the line 72. The composite WDMsignal is then shown passing through post-amplifier 74 and then appliedto the tandemly-positioned line amplifiers 58. Analogously, thedemultiplexer 64 includes a pre-amplifier 78 to which optical data isapplied, by way of the amplifiers 58 and in-line with the demultiplexerelement 82 of the demultiplexer 64. The demultiplexer operates togenerate individual optical data channels on the lines 84.

Certain of the lines 68 and certain of the lines 84 includehigher-performance transponders 86 that are less susceptible totransmission impairments. These lines, optical fibers, define the newgeneration portions of the communication system while others of thelines 68 and 84 define the legacy network parts of the communicationsystem. Communication stations 12 and 14 are coupled to lines 68 and 84of the legacy part of the communication system. And, communicationstations 16 and 18 are coupled to lines 68 and 84 of the new networkpart of the communication system.

During operation, the multiplexer multiplexes data generated on thelines 68 so that a resultant signal, provided by way of the lines 26 tothe regenerator, include data communicated upon multiple channels. Thedata generated on certain of the channels is communicated by way of thelegacy part of the system, and data communicated upon others of thechannels is communicated by way of a new network part of thecommunication system. Due to the differing communication requirements ofthe different parts of the communication system, only the datacommunicated by way of the legacy part, here represented bycommunications of data between the communication stations 12 and 14,need to be regenerated by the regenerator 24. Data communicated by wayof the new network part, here represented by data communicated betweenthe communication stations 16 and 18, need not be regenerated by theregenerator.

Pursuant to an embodiment of the present invention, apparatus, hereforming a by-pass part, 87 is connected in parallel with theregenerator. The bypass part is connected to the regenerator by way ofthe paths 52 and 54 which include, or form, couplers 44 & 46. Theapparatus 87 includes a bypass element 88, formed of an opticalinterleaver. The optical interleaver is of characteristics to passcertain wavelengths of energy. The interleaver is positioned to receivethe optical data provided on the line 26 by way of the splitter 44. Dueto the characteristics of the interleaver, portions of the optical dataare passed therethrough while other portions of the optical data areblocked. The data channels blocked by the interleaver correspond tothose regenerated by O-E-O converters 38. Through appropriate selectionof the channels upon which the data communicated in the legacy and newnetwork parts of the optical communication system and selection of thecharacteristics of the interleaver, legacy-network-communicated data iscaused to be passed through the regenerator, andnew-network-communicated data is caused to bypass the regenerator by wayof the bypass part. The data that must be regenerated is therebyregenerated, and the data that need not be regenerated is bypassed aboutthe regenerator.

The bypass part of the exemplary implementation may further include amultiplexer or optical combiner 92 positioned in-line with theinterleaver and with the path 54. Use of the multiplexer or opticalcombiner permits for future channel growth through connection throughpaths 94 and 96, respectively.

Wavelengths which are blocked from by-passing the regenerator by theinterleaver may be present on output 94 and channels which are presentedat input 96 will be multiplexed into the WDM stream 28. Ports 94 and 96therefore provide an expansion port which can be used for adding ordropping wavelengths at the regenerator site.

FIG. 2 illustrates the signal energy generated upon a set ofcommunication channels, identified as a new channel 102 and a legacychannel 104 during operation of the optical communication systempursuant to an embodiment of the present invention. The signal energygenerated upon the channel 102 is representative of data communicatedupon the new-network part, such as data communicated between thecommunication stations 16 and 18 shown in FIG. 1. And, the signal energygenerated upon the legacy channel 104 is representative of datacommunicated in the legacy network part of the communication system,such as data communicated between the communication stations 12 and 14.When applied on the line 26, the signal energy of the new channel 102 ispassed through the bypass element while the signal energy on the legacychannel 104, here, is not passed through the bypass element. As notedabove, in one implementation, the energy of the legacy channel is alsopassed through the interleaver port. The signal energy at the outputside of the bypass element is present only on the new channel 102, andno signal energy is present on the legacy channel 104. Conversely, theoutput side of the regenerator, signal energy is present only upon thelegacy channel 104. No signal energy is present on the new channel 102.Paths extend from the bypass element and the regenerator on the lines 54and 28, respectively, to the multiplexer 46. The output of themultiplexer includes signal energy on both the new and legacy channels102 and 104.

FIG. 3 illustrates a representation, shown generally at 112,representative of operation of the communication system 10 pursuant toan embodiment of the present invention. Here, data is originated at thecommunication stations 12 and 14. Data originated at the communicationstation 12 is modulated upon legacy channels, indicated by the block114. And, data originated at the communication station 14 is modulatedupon new channels 116. Once modulated, the data is communicated, hereindicated by the segments 118 and 122, respectively. The data modulatedupon the separate channels are multiplexed, indicated by the block 124,at the multiplexer 62. The data is transported, here indicated by thesegment 126, to the regenerator and bypass element 24/86. Data that ismodulated onto new wavelengths is bypassed, here indicated by thesegment 128, around the regenerator, while the data modulated ontolegacy wavelengths is regenerated, here indicated by the block 132, atthe regenerator. Once regenerated, the legacy wavelengths and newwavelengths are recombined.

The optical data bypassed by the bypass element and regenerated by theregenerator, respectively, is demultiplexed, indicated by the block 136at the demultiplexer 64. And, the data is forwarded on to thecommunication stations 14 and 18, respectively.

FIG. 4 illustrates a method flow diagram, shown generally at 144,representative of the operation of an embodiment of the presentinvention. The method routes first optical data and second optical datain an optical network having a regenerator.

First, and as indicated by the block 146, the first optical data and thesecond optical data is routed to the regenerator. Then, and as indicatedby the block 148, the first optical data, routed to the regenerator, iscaused to bypass the regenerator and to follow a bypass route thatbypasses the regenerator.

And, as indicated by the block 152, routing of the second optical datais regenerated at the regenerator.

Thereby, through operation of an embodiment of the present invention, amanner is provided by which to facilitate communications in an opticalcommunication system. Data communicated in a network portion of theoptical communication system requiring lower transmission impairments iscaused to be provided to a regenerator while data not requiringregeneration for its communication bypasses the regenerator.

The previous descriptions are of preferred examples for implementing theinvention, and the scope of the invention should not necessarily belimited by this description. The scope of the present invention isdefined by the following claims.

1. Apparatus for an optical network having a regenerator to which firstoptical data is routed and to which second optical data is routed, saidapparatus comprising: an optical bypasser positioned in-line with pathsupon which the first optical data and the second optical data are routedand in parallel with the regenerator, said optical bypasser configuredto route the first optical data therethrough, thereby to cause the firstoptical data to bypass the regenerator; and a recombiner positionedin-line with said optical bypasser and the regenerator, said recombinerconfigured to recombine routing paths of the first optical data,bypassed around the regenerator, and the second optical data,regenerated by the regenerator.
 2. The apparatus of claim 1 wherein saidoptical bypasser comprises an optical interleaver.
 3. The apparatus ofclaim 1 wherein the first optical data exhibits first characteristicsand the second optical data exhibits second characteristics, the firstcharacteristics exhibited by the first optical data permitting routingthereof through said optical bypasser.
 4. The apparatus of claim 3wherein the second characteristics exhibited by the second optical dataprevent routing thereof through said optical bypasser.
 5. The apparatusof claim 1 wherein the first optical data and the second optical dataare wavelength division multiplexed and are communicated at separateoptical frequencies.
 6. The apparatus of claim 1 wherein third opticaldata and fourth optical data are further routed to the regenerator, andwherein said optical bypasser is further configured to route the thirdoptical data therethrough.
 7. The apparatus of claim 1 wherein theregenerator comprises a set of couplers and wherein said opticalbypasser is positioned in-line with the regenerator by connection to thecouplers.
 8. The apparatus of claim 7 wherein said recombiner comprisesan optically conductive path extending between said optical bypasser andthe regenerator.
 9. The apparatus of claim 1 further comprising amultiplexer having a set of input terminals and an output terminal, afirst input terminal of the set of input terminals connected to saidoptical bypasser to be provided with the first optical data, bypassed byway of said optical bypasser and the output terminal connected to saidrecombiner, wherein additional optical data may be added by input to asecond input terminal in the set of input terminals.
 10. The apparatusof claim 1 wherein said optical bypasser further comprises an expansionport and wherein said optical bypasser is further configured to routethe second optical data to the expansion port.
 11. The apparatus ofclaim 1 wherein the first optical data is communicated via lineterminating equipment having first transmission performancecharacteristics, wherein the second optical data is communicated vialine terminating equipment having second transmission performancecharacteristics.
 12. The apparatus of claim 1 wherein said opticalby-passer routes alternate channels on an evenly spaced wavelength gridto the regenerator and to the optical regenerator bypasser.
 13. A methodfor routing first optical data and second optical data in an opticalnetwork having a regenerator, said method comprising the operations of:routing the first optical data and the second optical data to theregenerator; causing the first optical data, routed to the regenerator,to bypass the regenerator and follow a bypass route that bypasses theregenerator; and, permitting routing of the second optical data throughthe regenerator.
 14. The method of claim 13 further comprising theoperation of regenerating the second optical data at the regenerator.15. The method of claim 14 further comprising the operation ofrecombining the first optical data, bypassed about the regenerator, andthe second optical data, once regenerated at the regenerator.
 16. Themethod of claim 13 wherein the first optical data and the second opticaldata, when routed to the regenerator are wavelength division modulated.17. The method of claim 13 wherein said operation of causing the firstoptical data to bypass the regenerator comprises processing the firstand second optical data by an optical interleaver which provides opticaldata of alternating channels to bypass the regenerator, and routing thedata of the alternating channels around the regenerator.
 18. The methodof claim 13 wherein said operation of causing the first optical data tobypass the regenerator comprises causing optical data of even wavelengthchannels to bypass the regenerator, the first optical data modulated atthe even wavelength channels.
 19. The method of claim 18 wherein saidoperation of permitting routing comprises permitting routing of opticaldata of odd wavelength channels, relative to the even wavelengthchannels, the second optical data modulated at the odd wavelengthchannels.
 20. A method for an optical communication system having afirst network part permitting communication of optical data when theoptical data is of at least first transmission characteristics andhaving a second network part permitting communication of optical datawhen the optical data is of at least second transmission characteristic,the first signal transmission characteristics allowing for greatertransmission distance than the second signal transmissioncharacteristics, the first and second network parts, respectively,extending to a regenerator, said method comprising: modulating theoptical data communicated in the first network part upon first opticalchannels; modulating the optical data communicated in the second networkpart upon second optical channels; routing the data of the first opticalchannels around the regenerator; and regenerating the data of the secondoptical channels at the regenerator.
 21. The method of claim 20, whereinsaid first and second optical channels are alternate channels on awavelength grid, and said routing includes providing the first andsecond optical channels to an optical interleaver, wherein the opticalinterleaver routes alternate channels on a wavelength grid, routing thefirst optical channels around the regenerator.
 22. The method of claim20, wherein the alternating channels are even numbered wavelengthchannels alternating with odd numbered wavelength channels.
 23. Theapparatus of claim 2, wherein the first optical data is modulated uponfirst optical channels, the second optical data is modulated upon secondoptical channels, said first and second optical channels are alternatechannels on a wavelength grid, and said optical interleaver routesalternate channels on a wavelength grid, routing the first opticalchannels to bypass the regenerator.